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新型搅拌棒式微萃取器萃取气相色谱法分析蔬菜中毒死蜱残留量 总被引:1,自引:1,他引:0
用自制新型搅拌棒式微萃取器吸着萃取、溶剂解吸,结合配有电子捕获检测器(ECD)的气相色谱分析蔬菜中毒死蜱残留量,以此建立一种快速、简单而准确的分析方法。对影响萃取的重要参数如萃取时间、解吸时间、解吸溶剂等进行了优化。该方法在1-500ng/L有很好的线性,线性相关系数为0.9914,最低检测限为0.3ng/L。用50ng/L的毒死蜱标准品做重现性实验,其RSD低于6.7%(n=5)。并对实际蔬菜样品进行了分析,结果令人满意。 相似文献
74.
采用正交法考察了各因素对葛根素纯化工艺的影响,确立了离子交换纤维纯化葛根素的最佳工艺.结果表明:强碱阴离子交换纤维吸附葛根素的最佳条件是上药液的pH=7,药液流速0.17 mL/min,药液质量浓度为1.6 mg/mL,溶剂为75%的乙醇.吸附在强碱阴离子交换纤维上的葛根素动态解吸的最佳条件是乙酸浓度为2.5 mol/L,解吸液体积与纤维床体积的比值为8.实验结果表明用强碱阴离子交换纤维纯化葛根素是可行的. 相似文献
75.
煤层气是储集在煤层中的非常规天然气.煤层中发育有微孔隙系统和裂隙系统,煤层气主要以物理吸附的形式赋存于煤的内表面上,当压力降低时,煤层气发生解吸、扩散和渗流,最后由井筒中产出.了解煤层气的赋存、运移机理及产出特征,对进行煤层气的可采性评价十分重要. 相似文献
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Using soybean hull residue after the soluble dietary fiber being removed during the soybean processing industry as crude material, a novel absorbent modified soybean hulls is prepared. Its adsorption behavior for Pb2+ is studied. The adsorbent has a large and efficient adsorpuon capacity for Pb-, uv to 20% of the mass of dry adsorbent. Its maximum adsorption capacity for Pb2+ reaches 217 mg.g-1 at initial Pb2+ concentration of 2000 mg.L-1,which is twice that of yeast absorbent and threefold greater than that of chitosan absorbent. The adsorption ability is sensitive to pH value in the solution and the optimal pH for adsorption of Pb2+is 7.0. In the presence of other metal ions (Ca2+, Mg2+and Na+) in the solution, their effect on the adsorption capacity for Pb2+is not obvious. After 5 cycles of adsorption, 80% adsorption capacity of Pb2+ is maintained. Compared with various available commercial resins, the modified soybean hulls are a plentiful, inexpensive and effective medium for the capture of dissolved Pb2+ from waste streams. 相似文献
78.
The molecular morphology of thin gelatin films, controlled through the casting temperature, was monitored by wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). Gelatin films dried at lower temperatures had a markedly higher crystalline or helical structure with a slightly higher Tg and lower ΔCp compared with hot dried films, which had a more coiled structure. The relationship between molecular morphology and gelatin-water interaction in terms of hydration behavior and water diffusivity was assessed using dynamic vapor sorption (DVS). The sorption capacity increased and the level of hysteresis decreased with increasing the degree of crystallinity. The difference in the aging behavior of the films was explained in terms of the difference between the glass transition and aging temperatures, (Tg – Ta). 相似文献
79.
Fang‐Yuan Fan Quan Gan Zhan‐Bo Dong Kwan‐Jeong Song Xin‐Qiang Zheng Yue‐Rong Liang Jian‐Liang Lu 《International Journal of Food Science & Technology》2014,49(7):1626-1634
Desorption of catechins and caffeine from polyvinylpolypyrrolidone (PVPP) was comprehensively investigated. The result showed that caffeine could easily be desorbed from PVPP by the tested solvents except n‐hexane, while catechins could only be thoroughly done by dimethyl sulphoxide (DMSO) and N, N‐dimethylformamide (DMF). Excellent desorption efficiency of DMSO and DMF might be attributed to their high dipole moments and H‐bond potentials. Addition of ethanol was recommended considering the elution efficiency and fluidity, but ethanol volume should be <40% (v/v) for DMSO or 20% (v/v) for DMF. Desorption would get to equilibrium within 1 h and followed the pseudo‐second‐order model. Caffeine and catechins could be separately desorbed through two‐stage elution procedure, that is, water or 20% aqueous ethanol for desorbing caffeine and part of nongalloylated catechins and DMSO/ethanol (8/2, v/v) for eluting the remaining catechins. Highly purified catechins (~95%) with high level (~70%) galloylated catechins would be achieved when the desorption procedure was applied in column chromatograph. 相似文献
80.
Marko Jovanovi? Richard Tyldesley-Worster Gottfried Pohlentz Jasna Peter-Katalini? 《International journal of molecular sciences》2014,15(4):6527-6543
Human milk oligosaccharides (HMO) represent the bioactive components of human milk, influencing the infant’s gastrointestinal microflora and immune system. Structurally, they represent a highly complex class of analyte, where the main core oligosaccharide structures are built from galactose and N-acetylglucosamine, linked by 1–3 or 1–4 glycosidic linkages and potentially modified with fucose and sialic acid residues. The core structures can be linear or branched. Additional structural complexity in samples can be induced by endogenous exoglycosidase activity or chemical procedures during the sample preparation. Here, we show that using matrix-assisted laser desorption/ionization (MALDI) quadrupole-time-of-flight (Q-TOF) collision-induced dissociation (CID) as a fast screening method, diagnostic structural information about single oligosaccharide components present in a complex mixture can be obtained. According to sequencing data on 14 out of 22 parent ions detected in a single high molecular weight oligosaccharide chromatographic fraction, 20 different oligosaccharide structure types, corresponding to over 30 isomeric oligosaccharide structures and over 100 possible HMO isomers when biosynthetic linkage variations were taken into account, were postulated. For MS/MS data analysis, we used the de novo sequencing approach using diagnostic ion analysis on reduced oligosaccharides by following known biosynthetic rules. Using this approach, de novo characterization has been achieved also for the structures, which could not have been predicted. 相似文献